J/ApJ/669/959 Warm molecular hydrogen in SINGS galaxy sample (Roussel+, 2007)
Warm molecular hydrogen in the Spitzer SINGS galaxy sample.
Roussel H., Helou G., Hollenbach D.J., Draine B.T., Smith J.D., Armus L.,
Schinnerer E., Walter F., Engelbracht C.W., Thornley M.D., Kennicutt R.C.,
Calzetti D., Dale D.A., Murphy E.J., Bot C.
<Astrophys. J., 669, 959-981 (2007)>
=2007ApJ...669..959R 2007ApJ...669..959R
ADC_Keywords: Surveys ; Galaxies, IR ; Interstellar medium ; Spectroscopy
Keywords: galaxies: ISM - infrared: galaxies - infrared: ISM -
ISM: lines and bands - ISM: molecules - surveys
Abstract:
Results on the properties of warm molecular hydrogen in 57 normal
galaxies are derived from measurements of H2 rotational transitions,
obtained as part of SINGS. This study extends previous extragalactic
surveys of emission lines of H2 to fainter and more common systems
(LFIR = 107-6x1010L☉). The 17um S(1) transition is securely
detected in the nuclear regions of 86% of galaxies with stellar masses
above 109.5M☉.
Description:
The SINGS sample (Kennicutt et al., 2003PASP..115..928K 2003PASP..115..928K), comprising
75 galaxies, is intended to be a valuable representative set of local
galaxies that are not ultraluminous, and whose moderate distances
ensure that the properties of the interstellar medium can be studied
at relatively small spatial scales (a few hundreds of parsecs at the
shortest wavelengths).
To estimate flux densities of the dust continuum and of the aromatic
bands (also referred to as the emission from PAHs, or polycyclic
aromatic hydrocarbons), we used images in the 3.6 and 7.9um bands
of the IRAC camera and scan maps in the three bands of the MIPS
instrument at effective wavelengths of 24, 71, and 156um.
The targets were observed in mapping mode with the IRS instrument, at
low spectral resolution between 5 and 38um, with the SL and LL slits
(resolution ∼60-130), and at high spectral resolution between
10 and 37um, with the SH and LH slits (rsolution ∼600).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 52 66 Targets
table3.dat 88 66 Fluxes
table4.dat 61 153 Derived temperatures, column densities and
high temperature ortho to para ratio (OPRhighT)
table5.dat 77 66 Masses in the warm and cold phases
refs.dat 67 37 References
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Galaxy name
9 A1 --- n_Name [ab] Note on Name (1)
11- 14 F4.1 Mpc Dist Distance from Kennicutt et al.
(2003PASP..115..928K 2003PASP..115..928K)
16- 20 A5 --- Class Nuclear classifications (2)
24- 25 I2 h RAh Right ascension (J2000)
27- 28 I2 min RAm Right ascension (J2000)
30- 34 F5.2 s RAs Right ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 46 F4.1 arcsec DEs Declination (J2000)
48- 52 F5.1 arcsec+2 Apert Solid angle of the apertureAover which
spectra were extracted.
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Note (1): Notes as follows:
a = A total of 11 extranuclear regions were observed in
high-resolution spectroscopy in NGC 5194, from which
we included seven in our sample.
b = Several locations were observed in high-resolution spectroscopy
in this galaxy. We present here results for three among the
brightest regions at 7.9 and 24um.
N6822_A corresponds to the H II region Hubble V ([H25] V in
Simbad) (Hubble 1925ApJ....62..409H 1925ApJ....62..409H), and
N6822_C to the H II region Kgamma ([KGM79] gam in Simbad)
(Kinman et al. 1979PASP...91..749K 1979PASP...91..749K).
Note (2): derived from optical spectroscopy, published by Smith et al.
(2007, Cat. J/ApJ/656/770), were modified for the following targets.
N1097, N1512, N4321, and N7552: since our aperture includes a bright
star-forming ring, which dominates the dust and line emission, we
adopt the H II class instead of the LINER class. N2841, N4552, N4569,
N4594, N4826, and N5195: the Sy class was changed to LINER (Ho et al.
1997, Cat. J/ApJS/112/315). N3198 and N3938: the LINER class was
changed to H II (Ho et al., 1997, Cat. J/ApJS/112/315). The dwarf
galaxy class is here arbitrarily defined by a total stellar mass,
estimated by Lee et al. (2006ApJ...647..970L 2006ApJ...647..970L) as below
109.7M☉.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Galaxy name
9 A1 --- H [abc] higher-level H2 transitions observed (3)
11- 15 F5.1 aW/m2 S(0) H2 S(0) rotational transition flux
17- 21 F5.1 aW/m2 e_S(0) Error in S(0) rotational transition flux
23- 27 F5.1 aW/m2 S(1) H2 S(1) rotational transition flux
29- 32 F4.1 aW/m2 e_S(1) Error in S(1) rotational transition flux
34- 38 F5.1 aW/m2 S(2) H2 S(2) rotational transition flux
40- 43 F4.1 aW/m2 e_S(2) Error in S(2) rotational transition flux
45- 49 F5.1 aW/m2 S(3) H2 S(3) rotational transition flux
51- 54 F4.1 aW/m2 e_S(3) Error in S(3) rotational transition flux
56- 61 F6.1 aW/m2 [SiII] The [SiII] (34.8um) flux
63- 67 F5.1 aW/m2 e_[SiII] Error in [SiII]
69- 73 F5.3 Jy F7.9 PAH flux density in IRAC 7.9um band
75- 79 F5.3 Jy F24 MIPS 24 micron band flux density
81- 84 I4 fW/m2 FIR Total estimated infrared flux density (4)
86- 88 I3 fW/m2 e_FIR Error in FIR
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Note (3): For NGC1266, NGC4569 and NGC4579, it was possible to measure
higher-level transitions of H2, which are provided as follows:
a = The S(4) to S(7) line fluxes are respectively: (102.7±17.4),
(241.9±19.9), >18.5 and (192.2±28.6) times 10-18W/m2.
The S(6) transition was not accurately measurable because it was
observed at low spectral resolution on the blue shoulder of a
bright 6.2µm aromatic band.
b = The S(4) to S(7) line fluxes are respectively: (52.6±27.7),
<252.6, <61.3 and (50.3±24.2) times 10-18W/m2. The S(5) and
(6) transitions are upper limits because S(5) is contaminated by
the [ArII] line at 6.985µm and S(6) is diluted in the blue
shoulder of the 6.2µm aromatic band.
c = The S(4) to S(7) line fluxes are respectively: (48.7±10.7),
<324.9, <147.2 and (83.3±37.5) times 10-18W/m2. The same
remark as for NGC4569 applies.
Note (4): Between 3 and 1100µm, defined as a linear combination of 24,
71 and 156µm flux densities.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Galaxy name (1)
9 A1 --- f_Name [abc] Flag on name (2)
11 A1 --- l_T1 Limit flag on T1
12- 14 I3 K T1 Lower temperature component
16 A1 --- l_f1 Limit flag on f1
17- 23 F7.5 --- f1 Discrete component mass fraction at T1
25 A1 --- l_T2 Limit flag on T2
26- 29 I4 K T2 Upper temperature component
31 A1 --- l_f2 Limit flag on f2
32- 38 F7.5 --- f2 Discrete component mass fraction at T2
40- 43 F4.2 --- OPR ? Ortho to para ratio in the
high-temperature limit
45- 48 F4.2 --- e_OPR ? Uncertainty in OPR
50- 56 F7.3 10+20/cm2 Ntot Total H2 column density for T>T1
58- 61 F4.2 --- RNtot ? Ratio of the total H2 column densities,
Ntot(OPR=3)/Ntot(OPR<3)
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Note (1): For each galaxy, the first line gives the results of the fits
where T1 is constrained in order not to overestimate the column
density, and the second (third) line where T1 is unrestricted. For
galaxies where the S(2) flux is an upper limit, only constrained-T1
fits were performed. When OPRhighT<3, T2 is fixed, and the free-T1
fit results are then provided for two different values of T2:
1.14*T(S1-S3) (second line) and 1.5*T(S1-S3) (third line). See Section
3.2 for explanations.
Note (2): Notes as follows:
a = The third component is characterized by T3=1415K and f3=0.00690
(constrained-T1 fit) or T3=1455K and f3=0.00477 (free-T1 fit)
b = Where T3=1139K and f3=0.00088 (constrained-T1 fit), or T3=1319K
and f3=0.00019 (free-T1 fit)
c = Where T3=1324K and f3=0.00561 (constrained-T1 fit), or T3=1414K
and f3 = 0.00010 (free-T1 fit)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Galaxy name (5)
9 A1 --- n_Mass [ab] Note for Mrk 33 and NGC 4559 (6)
11- 18 F8.4 10+6solMass Mass H2 mass for T>T1
20 A1 --- l_Ntot Limit flag on Ntot
21- 25 F5.1 10+20mol/cm2 Ntot ? Total cold H_2 column density
27 A1 --- l_RMass Limit flag on RMass
28- 32 F5.3 --- RMass ? Mass ratio, M(T>T1)/M(cold H2)
34- 37 I4 arcsec2 CObeam ? The CO beam solid angle
39- 42 F4.2 --- Corr ? CO intensity correction (7)
44- 47 A4 --- Map Map used to derive Corr (see Section 4)
49- 77 A29 --- Ref The CO reference, in refs.dat file
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Note (5): We retain here results from constrained-T1 fits, giving lower
masses in the warm phase. Whenever the excitation diagrams are
ambiguous regarding the value of OPR_high T_, we adopt the mass of
warm H2 derived with OPRhighT<3, which is also smaller than the
mass derived with OPRhighT=3 (see Table 4).
Note (6): Notes as follows:
a = For Mrk 33, the H2 mass fraction in the warm phase may be
severely overestimated in this blue compact galaxy, because of
the use of an inappropriate factor to convert CO flux to total
H2 mass. Israel (2005A&A...438..855I 2005A&A...438..855I) derive a factor about
four times higher than the standard factor used here, which
would make the total H2 mass also four times higher.
NGC 6822_A: In their detailed study of this region, Israel et al.
(2003A&A...397...87I 2003A&A...397...87I) derive a CO flux to total H2 mass
conversion factor twenty times higher than the standard factor,
so that the same remark as for Mrk 33 applies.
b = NGC 4559 has the highest mass fraction in the warm phase, even
when constraining T1 to be near-maximal. The warm phase is
dominated by gas at ∼100K.
NGC 4559 is a quiescent galaxy, as obvious from the low
F24/F7.9 flux density ratio within the IRS aperture. The
galaxy has little molecular gas, and it is possible that it is
mostly diffuse, and thus more exposed to FUV radiation. The same
remarks may apply, to a lesser degree, to other galaxies of the
sample such as NGC 628.
Note (7): The factor that was applied to the CO brightness in order to
correct for the different apertures of the CO and H2 observations.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Ref Reference code
6- 24 A19 --- BibCode BibCode
26- 45 A20 --- Aut Author's name
47- 67 A21 --- Com Comments
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 27-Jan-2010